During execution of a software module, a microprocessor executes software instructions associated with the module. Each instruction may call upon the microprocessor to perform some task. A plethora of possible tasks exists. For example, some tasks include moving data to or from a storage medium or register, performing various mathematical or data processing tasks, controlling portions of the microprocessor or other devices, monitoring various parameters, and responding to interrupts and other messages.
In performing a task, a microprocessor utilizes one or more hardware functional units (e.g., a floating-point unit). Some functional units are called upon frequently, and others are called upon rarely. Regardless of the frequency of their use, the functional units are maintained in a powered-up state while the microprocessor is actively executing a module. This enables a functional unit to be ready for use when an instruction that requires the functional unit is executed by the microprocessor.
Each functional unit consumes a certain amount of power. Some power is consumed while the functional unit is perfoiining a task or waiting to perform a task, and some power is dissipated through leakage. In portable devices, this power often is supplied from a battery source. Because the amount of power that a battery can supply between charges is limited, the amount of time that a system can be used between charges also is limited. For example, a laptop computer battery may only be able to provide one or two hours worth of use before a recharge is needed.
Battery life is an increasingly important consideration in the portable device marketplace. For this reason, designers increasingly concern themselves with reducing power consumption and dissipation within electronic systems. Accordingly, what are needed are methods and apparatus that reduce power dissipation within an electronic system. Further needed are methods and apparatus that reduce power dissipation within an electronic system, which includes multiple functional units used by a processor to execute software instructions.